Automatic sprinkler systems are used extensively in buildings and the like for the purpose of providing a supply of fire extinguishing fluid such as water which will automatically be released by the system when the system is exposed to a predetermined elevated temperature at which the system is designed to be activated. Such automatic sprinkler systems generally include conduits supplied with a fire extinguishing fluid under pressure, and a plurality of automatic sprinkler heads which are individually fitted in the conduits and which include a normally closed valve member and a temperature responsive element that will permit the valve member to be opened by the fluid pressure in the supply conduit when a predetermined temperature is reached, thereby resulting in the fire extinguishing fluid being dispersed throughout a surrounding area.
One of the most commonly used temperature responsive elements is a frangible bulb made of quartz and filled with a bursting charge of fluid which will expand and burst the frangible bulb when the temperature of the charge is raised to a predetermined level, a frangible bulb of this type being disclosed in U.S. Pat. No. Re. 16,132. Such frangible bulbs are generally mounted in a sprinkler head frame so as to bear against a valve member and hold the valve member in place and thereby close the bore at which pressurized fire extinguishing is present, typical arrangement of this sort being described in U.S. Pat. Nos. 2,046,169 and 2,528,063.
The aforementioned frangible bulbs are quite reliable in operation but care must be exercised in providing a suitable mounting for the bulb because of the frangible nature of the bulb and the fact that the bulb must be able to withstand and transmit to the valve member a force that is sufficient to maintain the valve member at its closed position in the frame bore in opposition to the pressure exerted against the valve member by the pressurized fire extinguishing fluid (e.g. 500 psi). Additionally, the frangible bulb must be mounted in such a way that it will not inadvertently break when the sprinkler head is subjected to relatively minor shocks and vibrations, such as might be expected during installation of the sprinkler head.
In an effort to overcome the aforementioned difficulties encountered in properly mounting a frangible bulb in a sprinkler head, some prior art sprinkler heads, such as that shown in U.S. Pat. No. 2,469,832, utilized a plurality of separable liners and gaskets which are made from a metal such as copper and which are disposed between the valve member and the frangible bulb, and between the valve member and its seat, to soften somewhat the effect of the compressive force exerted against the bulb and to increase the sealing capacity of the valve member. However, these copper liners and gaskets increase the cost of the sprinkler heads, and they render assembly of the sprinkler head more difficult, and the metal-to-metal sealing contact is sometimes ineffective, particularly when the fire extinguishing fluid is under a relatively high pressure.
It has also been heretofore proposed to provide the sprinkler head with a valve member having a built-in, relatively complex spring assembly such as disclosed in U.S. Pat. No. 1,996,077, to provide a resilient mounting for the frangible bulb, and a metal gasket is provided at the valve seat to increase the sealing characteristics of the valve member. Such complex valve member constructions are relatively expensive to produce, and somewhat difficult to assemble in place.
Finally, U.S. Pat. No. 3,253,657 discloses a sprinkler head having a frame formed with a flexible, annular protrusion that provides a yieldable flange for supporting a valve body made from Teflon and including a sealing ring that engages the annular protrusion of the frame. While the valve member itself has a simple construction, the frame must be specially formed with the thin annular protrusion, and this protrusion is vulnerable to breakage, particularly during shipment and installation of the sprinkler head.
By substantial contrast, the sprinkler head of the present invention is extremely simple and inexpensive to produce, yet it is very reliable and it combines excellent sealing characteristics with a yieldable support for the frangible bulb.